A. Field of Invention
This invention relates to a method and apparatus for grinding stumps with an elongated grinding tool rotatable about a generally vertical axis. The tool is mounted on a supporting vehicle and may be self powered or the supporting vehicle may provide power for rotating the tool. Piston cylinder assemblies on the vehicle provide vertical movement of the grinding tool into and out of the ground adjacent the stump and horizontal movement along the sides of the stump for grinding the stump.
B. Description of Related Art
Stump grinders of the type shown in applicant""s U.S. Pat. No. 6,435,234 have disc cutters rotatable about a generally horizontal axis and are moved through the stump in a direction parallel with the axis of the cutter. This has the disadvantage of the drive shaft and bearings being below the ground level where they are exposed to dirt and rocks. Also, the debris which may include stones thrown out of the hole in the ground which constitutes a safety problem.
Another problem with disc cutter rotatable about a horizontal axis is that they require relatively large diameter disc cutters in order to grind deep enough to remove the roots of medium and large stumps. The large diameter disc cutters also require more power which cannot be supplied by small horsepower vehicles. The large diameter discs also may climb up on the stump being ground and upset the vehicle on which they are mounted.
Stump grinding tools rotatable about a vertical axis have been proposed as shown in U.S. Pat. Nos. 1,012,962 and 1,466,538 where the grinding tools are placed over the stump and grind it down to ground level. These patents including U.S. Pat. No. 3,818,957 which has a grinding tool rotatable about a vertical axis are directed to brush and tree cutting for land clearing and not to stump removal. Also, as stated in U.S. Pat. No. 3,818,957 xe2x80x9ca shroud can be affixed to the outer portions of these elongate blades to retain dirt or earth removed by the blades at the sightxe2x80x9dxe2x80x94This clearly indicates the grinding is done above the ground and not below the ground.
The present invention is directed to a stump grinder having an elongated grinding tool rotatable about a vertical axis for drilling into the ground adjacent a stump to a position below the ground and then moving horizontally into the sides of the stump where the debris and stones are thrown horizontally below the ground around the grinding tool. The debris which may be ejected above the ground is ground wood which does not constitute a serious hazard as do the stones which are located below the ground.
The grinder may be attached to equipment such as a skid steer vehicle, an articulated rubber tired vehicle or a hydraulic excavator which provide a source of adequate power including internal combustion engines, electric power or the addition of PTO power hydraulic drive power to rotate the grinding tool.
In accordance with one aspect of the invention there is provided a stump grinding apparatus comprising a grinding tool support member, an elongated grinding tool mounted on the support member for rotation about a generally vertical axis of rotation, power means mounted on the support member and connected to the grinding tool for rotating the grinding tool, cutting teeth mounted on a stump grinding surface of the grinding tool, means to lower the support member and drive the rotating grinding tool into the ground at a position adjacent the stump, means to move the supporting member in a generally horizontal direction towards the stump to urge the rotating grinding tool and the cutting teeth of the stump grinding surface into a side of the stump underground, means to oscillate and curl the supporting member to move the grinding tool stump grinding surface along the buried surfaces of the stump to grind away the stump, and means to raise the support member to remove the grinding tool from the ground.
In accordance with another aspect of the invention there is provided a method of grinding a tree stump underground with an elongated generally cylindrical rotatable grinding tool having cutting blades on the generally cylindrical stump grinding surface of the tool comprising supporting an upper end of the grinding tool on a supporting member for rotation about a vertical axis, rotating the grinding tool by power means connected to an upper end of the grinding tool, lowering the grinding tool into the ground at a position adjacent the stump for penetrating the ground to a depth adjacent the roots of the stump, moving the grinding tool towards the stump to engage the sides of the stump, traversing the grinding tool along the sides of the stump to grind away portions thereof, raising the grinding tool out of the ground after the stump is ground away and stopping rotation of the grinding tool.